Update git package to include 2.11.1 (#3020)
Update git package to include 2.11.1 (#3020)

Add git v2.11.1 digest.

Built and lightly tested on CentOS 7.
iulian787/spack,LLNL/spack,iulian787/spack,tmerrick1/spack,iulian787/spack,mfherbst/spack,iulian787/spack,lgarren/spack,mfherbst/spack,matthiasdiener/spack,EmreAtes/spack,lgarren/spack,skosukhin/spack,mfherbst/spack,krafczyk/spack,skosukhin/spack,tmerrick1/spack,matthiasdiener/spack,LLNL/spack,EmreAtes/spack,EmreAtes/spack,tmerrick1/spack,skosukhin/spack,krafczyk/spack,krafczyk/spack,matthiasdiener/spack,mfherbst/spack,tmerrick1/spack,TheTimmy/spack,lgarren/spack,EmreAtes/spack,matthiasdiener/spack,lgarren/spack,TheTimmy/spack,lgarren/spack,LLNL/spack,tmerrick1/spack,TheTimmy/spack,mfherbst/spack,LLNL/spack,krafczyk/spack,TheTimmy/spack,skosukhin/spack,EmreAtes/spack,skosukhin/spack,TheTimmy/spack,krafczyk/spack,iulian787/spack,matthiasdiener/spack,LLNL/spack